For the blanched hierba santa leaves: Bring the water, ascorbic acid, and salt to a rolling boil.
Meanwhile, set up an ice water bath large enough to hold all of the leaves.
Dip the leaves all at once into the boiling water. Make sure to fully submerge them in the water. Blanch the leaves for 7 to 10 seconds or until they are wilted.
Quickly remove the leaves from the boiling water and place them in the ice water bath, stirring them to cool them down quickly.
For the infused water: Blend all of the ingredients together. Adjust the sweetness if necessary by adding more sugar and stirring to dissolve.
Pass through a fine-mesh sieve and then through cheesecloth to obtain a liquid purée.
For the gelée: Melt the gelatin over a water bath or in a microwave, then stir it quickly into the infused water using a whisk. It is crucial that the water not be too cold; otherwise the gelatin will set quickly. Let the gelée cool to room temperature.